Effect of Temperature on Microwave Permeability of an Air-Stable Composite Filled with Gadolinium Powder (original) (raw)
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Procedia Engineering, 2017
The paper considers the application of mixing rules to the analysis of the microwave effective material parameters, the permittivity and permeability, of composites. It is suggested to perform the analysis in terms of the normalized inverse susceptibility defined as the volume fraction of inclusions divided by the effective dielectric or magnetic susceptibility of the composite. This allows the volume fraction dependence of the effective material parameters to be represented in a form that is convenient for the analysis, so that distinguishing features of the dependence become more pronounced and helpful for understanding the factors that affect the effective properties of the composite. The proposed approach is illustrated by the analysis of the measured data on the microwave material parameters of composites comprising Sendust powder with either spherical or platelet powder particles, and Permalloy powders with particles of the stone-like shape. The microwave material parameters are measured with paraffin-based composite samples in the 7/3-mm coaxial air-filled waveguide by the Nicolson-Ross-Weir technique. It is shown that for Sendust particles, the interaction between inclusions is low. For the composites comprising spherical particles, the Maxwell Garnet mixing rule is a good approximation of the volume fraction dependence of microwave permeability. For the platelet powder particles, the magnetic performance is governed by the Wiener mixing rule. For composites filled with Permalloy powder, the contribution of the interaction between inclusions to the effective permeability is essential. Therefore, the suggested approach allows the type of mixing rule suitable for description of material parameters of a given composite to be determined.
Microwave permeability of Co[sub 2]Z composites
Journal of Applied Physics, 2005
The microwave permittivity and permeability of Co 2 Z barium ferrite composite samples are measured as functions of frequency and volume fraction of the ferrite. Magnetostatic properties of the bulk ferrite are determined. This allows Snoek's law [J. L. Snoek, Physica 14, 204 (1948)] to be verified by comparing the microwave and magnetostatic Snoek's constants. The modification of Snoek's law for hexagonal ferrites suggested recently by Acher et al. [Phys. Rev. B 62, 11324 (2000)] is also verified. Acher's constant is found from microwave measurements to agree with the value calculated from the magnetostatic properties of bulk ferrite, but microwave and magnetostatic Snoek's constant do not agree. This may be attributed to the effect due to demagnetizing factors of ferrite inclusions that are not considered in the derivation of Snoek's and Acher's laws. The measured frequency-dependent permeability of composites satisfies the Lorentzian dispersion law and is consistent with the Maxwell Garnett approximation [J. C. Maxwell Garnett, Philos. Trans. R. Soc. London 203, 385 (1904)]. According to the theoretical analysis based on the Lorentzian dispersion law and the Maxwell Garnet mixing rule, both Snoek's and Acher's constants must be linear functions of the volume fraction, independent of whether microwave values of the constants are in agreement with the magnetostatic values. In contrast, the experimental measurements reveal a steady decrease of both constants with the volume fraction. The disagreement is discussed in terms of the influence of effective medium in composite on the inherent permeability of ferrite particles.
Microwave permeability of Co2Z composites
Journal of Applied Physics, 2005
The microwave permittivity and permeability of Co 2 Z barium ferrite composite samples are measured as functions of frequency and volume fraction of the ferrite. Magnetostatic properties of the bulk ferrite are determined. This allows Snoek's law [J. L. Snoek, Physica 14, 204 (1948)] to be verified by comparing the microwave and magnetostatic Snoek's constants. The modification of Snoek's law for hexagonal ferrites suggested recently by Acher et al. [Phys. Rev. B 62, 11324 (2000)] is also verified. Acher's constant is found from microwave measurements to agree with the value calculated from the magnetostatic properties of bulk ferrite, but microwave and magnetostatic Snoek's constant do not agree. This may be attributed to the effect due to demagnetizing factors of ferrite inclusions that are not considered in the derivation of Snoek's and Acher's laws. The measured frequency-dependent permeability of composites satisfies the Lorentzian dispersion law and is consistent with the Maxwell Garnett approximation [J. C. Maxwell Garnett, Philos. Trans. R. Soc. London 203, 385 (1904)]. According to the theoretical analysis based on the Lorentzian dispersion law and the Maxwell Garnet mixing rule, both Snoek's and Acher's constants must be linear functions of the volume fraction, independent of whether microwave values of the constants are in agreement with the magnetostatic values. In contrast, the experimental measurements reveal a steady decrease of both constants with the volume fraction. The disagreement is discussed in terms of the influence of effective medium in composite on the inherent permeability of ferrite particles.
Journal of Magnetism and Magnetic Materials, 2019
A new method of studying microwave magnetic properties of metal particles and films is developed. The method is based on measurements with swept frequency under magnetic bias in a coaxial line. Application of the technique is illustrated by the data obtained for two types of samples, washershaped rolls of thin ferromagnetic films and composites filled with flake Sendust particles. The treatment of the measured data is performed with an account for sample demagnetization and anisotropy. The values of the anisotropy field and the saturation magnetization of thin iron films are calculated considering demagnetization of the sample. Because of the anisotropy of the composite samples, permeability depends slightly on the length of samples, and the saturation magnetization and the anisotropy field cannot be determined.
Broadband Microwave Measurements of Relative Permittivity and Permeability of Materials
A short review of modern techniques for broadband microwave measuring complex permittivity and permeability of materials at broadband microwave frequencies has been presented. Classification of type of the measurement methods to extract the complex permittivity and permeability of bulk materials has been done in this paper. Mathematical models of all the above-mentioned measurement types of methods are reviewed. Advantages and disadvantages of existing measurement devices/systems are described according to the classification made. A new design of test devices for the measurement system operating in broadband microwave frequency range has been proposed. Measurement system on the basis of the proposed device can be used for a measuring the ordinary bulk materials, ferrites (including fully magnetized) and magnetic materials but much cheaper then one to be made. The system is much cheaper than a free space measurement system. The approach to define the permeability tensor of magnetic m...
Electromagnetic Characterization of Composite Materials and Microwave Absorbing Modeling
The aim of this article is to study the dielectric behavior (,) in microwaves domain of composites made with Epoxy Resin (RE), Carbon Black (CB), and Magnesium Titanate (MT) on a large band of frequency. This kind of composites is very solicited for applications and miniaturization of the components circuits (cavities, antennas, substrates, etc.) in hyperfrequency electronics. In this study we have also highlighted the effect of the fillers nature and their concentrations on the behavior of these composites. The results obtained by time domain spectroscopy (TDS) have revealed the strong dependence of complex permittivity of the composite materials on both the nature and the concentration of conductive environment. Low frequency analysis (500 MHz) has been investigated to determine the conductivity of composites which is related to the percolation phenomenon. Moreover, the comparison between experimental results and theoretical models shows that the modeling Lichtenecker law is applicable to the ternary mixture in this frequency range and is in accordance with the approach postulated by Bottreau.
Magnetic and Microwave Properties of Polycrystalline Gadolinium Iron Garnet
2017
The microwave loss in nanosized GdIG particles synthesized using mechanical alloying technique was investigated. There were very few of research on the microwave properties of nanosized particle GdIG and there is no attempt investigating on the material at C-band frequency range (4-8 GHz) and its correlation with the microstructure. Gadolinium (III) oxide and iron (III) oxide, αFe2O3 were used as the starting materials. The mixed powder was then milled in a highenergy ball mixer/mill SPEX8000D for 3 hours. The samples were sintered at temperature 1200 oC for 10 hours in an ambient air environment. The phase formation of the sintered samples was analyzed using a Philips X’Pert Diffractometer with Cu-Kα radiation. Complex permeability consisted of real permeability and magnetic loss factor were measured using an Agilent HP4291A Impedance Material Analyzer in frequency range from 10 MHz to 1 GHz. A PNA-N5227 Vector Network Analyzer (VNA) was used to obtain the information on ferromagne...
Journal of Magnetism and Magnetic Materials, 2018
A method to retrieve permeability of a metal inclusion from the measured constitutive parameters of a single composite sample of known structure and filling is developed. Treating constitutive parameters for a set of fillings increases accuracy of inclusion permeability determination and makes it possible to select the appropriate mixing model for the composite. The method is applied to determine microwave permeability of sendust inclusions from the measured permeability and permittivity spectra for a set of composites filled with sendust flakes and spheres. The calculations are performed for symmetric (Bruggeman type) and for matrix (Maxwell Garnett type) structures. The composites are shown to have the matrix structure. The retrieved permeability of inclusions is in good agreement with the data calculated with the parameters of generalized matrix mixing model that accounts for percolation threshold.
Technical Physics, 2009
The structure and microwave magnetic properties of Fe powders grounded in argon or acetone and also of Fe-Si-C and amorphous Fe-Co-Si-C powders mechanically alloyed in argon are studied using X-ray diffraction, Mössbauer spectroscopy, granulometric and microscopic analyses, magnetostatic measurements, and microwave spectroscopy. The goal of investigation is to determine the influence of factors (shape, size, and chemical and phase compositions of grains) governing the microwave material parameters of composites based on these alloys in the frequency range 0.1-3.0 GHz. It is shown that the difference in the grain shape is the basic reason for the difference in the microwave permeability at low frequencies (3 GHz or lower). At higher frequencies, the magnetic properties are related to the skin effect and depend largely on the grain size. The differences in the microwave properties of the composites are not significant and are concealed by the above effects. PACS numbers: 41.20.-q
Journal of Magnetism and Magnetic Materials, 2007
The complex permittivity (ε′–jε″), complex permeability (μ′–jμ″) and microwave absorption properties of ferrite–polymer composites prepared with different ferrite ratios of 50%, 60%, 70% and 80% in polyurethane (PU) matrix have been investigated in X-band (8.2–12.4 GHz) frequency range. The M-type hexaferrite composition BaCo+20.9Fe+20.05Si+40.95Fe+310.1O19 was prepared by solid-state reaction technique, whereas commercial PU was used to prepare the composites. At higher GHz frequencies, ferrite's permeabilities are drastically reduced, however, the forced conversion of Fe+3 to Fe+2 ions that involves electron hopping, could have increased the dielectric losses in the chosen composition. We have measured complex permittivity and permeability using a vector network analyzer (HP/Agilent model PNA E8364B) and software module 85071. All the parameters ε′, ε″, μ′ and μ″ are found to increase with increased ferrite contents. Measured values of these parameters were used to determine the reflection loss at various sample thicknesses, based on a model of a single-layered plane wave absorber backed by a perfect conductor. The composite with 80% ferrite content has shown a minimum reflection loss of −24.5 dB (>99% power absorption) at 12 GHz with the −20 dB bandwidth over the extended frequency range of 11–13 GHz for an absorber thickness of 1.6 mm. The prepared composites can fruitfully be utilized for suppression of electromagnetic interference (EMI) and reduction of radar signatures (stealth technology).